Particles from outside of the disk drive can come into the disk drive or the particles can originate from within the disk drive. In the latter case, the particles may result from parts wearing against each other, from lubricating oil that is inside of the disk drive, or result from inadequate washing of disk drive components, among other things. In order to store and read data, the read write head flies close to the surface of the disk. A particle that comes between the air bearing surface of the read write head and the surface of the disk can cause damage to the disk as well as the read write head. Thus, data can be permanently lost and the disk drive can be ruined.
Therefore, it has always been important to maintain as clean an environment inside the disk drive as possible. Typically, a filter has been placed inside of a disk drive in order to maintain a clean environment. FIG. 1 depicts a prior art disk drive with a conventional filter. The disk drive 110 includes a base casting 113, a motor hub assembly 130, a disk 112, actuator shaft 132, actuator arms 134, suspension assembly 137, a hub 140, rotary voice coil motor 150, a magnetic read write head 156, a slider 155, a desiccant 160, and a conventional filter 174.
The components are assembled into a base casting 113, which provides attachment and registration points for components and subassemblies. A plurality of suspension assemblies 137 (one shown) can be attached to the actuator arms 134 (one shown) in the form of a comb. A plurality of transducer heads or sliders 155 (one shown) can be attached respectively to the suspension assemblies 137. Sliders 155 are located proximate to the disk 112's surface 135 for reading and writing data with magnetic heads 156 (one shown). The rotary voice coil motor 150 rotates actuator arms 134 about the actuator shaft 132 in order to move the suspension assemblies 137 to the desired radial position on a disk 112. The desiccant 160 is typically placed near the voice coil motor 150. The actuator shaft 132, hub 140, actuator arms 134, and voice coil motor 150 may be referred to collectively as a rotary actuator assembly.
Data is recorded onto disk surfaces 135 in a pattern of concentric rings known as data tracks 136. A disk's surface 135 is spun at high speed by means of a motor-hub assembly 130. Data tracks 136 are recorded onto spinning disk surfaces 135 by means of magnetic heads 156, which typically reside at the end of sliders 155.
FIG. 1 being a plan view shows only one head, slider and disk surface combination. One skilled in the art understands that what is described for one head-disk combination applies to multiple head-disk combinations, such as disk stacks (not shown). However, for purposes of brevity and clarity, FIG. 1 only shows one head and one disk surface. One skilled in the art understands that what is described for a disk drive with a single disk applies to a disk drive with multiple disks. The embodied invention is independent of the number of head disk combinations.
The spinning of the disk 112 causes air to move inside of the disk drive 110. In order to position the read write head 156 at the appropriate location, it is important that the actuator 132 not be subjected to excessive air turbulence. One of the purposes of the bypass channel 168 is to reduce the amount of air that passes by the actuator 134. Air tends to flow along the bypass channel 168 as indicated by the arrows 170 rather than by the actuator 134, thus, reducing the amount of air turbulence that the actuator 134 is subjected to.
Since the read write head 156 flies close to the surface of the disk 112 any particle that comes between the read write head 156 and the surface 135 of the disk 112 could result in potentially permanent damage to the disk 112 and loss of data. Therefore, the conventional filter 172 is used for cleaning the air (also referred to herein as the “environment”) inside of the disk drive 110, thus, reducing the amount of particles inside of the disk drive 110. “Time to remove 90 percent of the particles” (also known as “T90”) is a common measurement for the ability of a filter to clean 90% of the particles out of the disk's environment.